Under the agreement, Celgene will add as much as $1.25 billion to the upfront payment if Impact’s drug fedratinib reaches approval milestones to treat myelofibrosis, a form of bone marrow cancer, and $150 million more for other indications. Additional payments could reach as much as $4.5 billion if global annual sales rise above $5 billion, according to a statement Sunday.

The total price would make Impact one of Celgene’s biggest acquisitions ever. The drugmaker is under increasing pressure to replace revenue from its top-selling cancer treatment before copycat medicines eat into Revlimid sales. Its stock lost more than a quarter of its value during a five-day stretch in October, after a highly anticipated drug for Crohn’s disease failed a late-stage trial and the drugmaker cut its 2020 profit target.

The shares haven’t recovered all of the lost ground, and as of Friday traded 28 percent below their 2017 peak of early October, giving Celgene a market value of about $83 billion. After news of the deal broke, shares climbed as high as $106.88 in premarket trading on Monday, and were recently up less than 1 percent at $105.80.

Jefferies analyst Michael Yee said in an email that the company “wisely structured” the deal to base much of its value on sales milestones, and isn’t overpaying for a late-stage asset.

Fedratinib is a kinase inhibitor that has shown promise as a potential treatment for a type of blood cancer called myelofibrosis, according to a statement put out by both companies.

“Myelofibrosis is a disease with high unmet medical need as the number of patients who are ineligible for or become resistant to existing therapy continues to increase,” said Nadim Ahmed, Celgene’s president of hematology and oncology.

“(Fedratinib) provides strategic options for us to build leadership in this disease.”

In October, Impact Biomedicines said it had raised funds to help get the drug to market. It treats the bone marrow cancers polycythemia vera and myelofibrosis.

Impact is readying manufacturing and logistics so the drug can be available immediately once it receives FDA approval. With strong evidence the drug works against the bone marrow cancers polycythemia vera and myelofibrosis, approval is likely, said John Hood, the company’s CEO, at the time of the investment from Oberland Capital.

Fedratinib was first developed by San Diego-based TargeGen, which French drugmaker Sanofi purchased in 2010 for up to $635 million on the drug’s promise.

But in 2013, just as clinical trials appeared to be successfully concluding, a few patients developed a neurological disorder. The FDA put a hold on development, and Sanofi immediately dropped the drug.

Fedratinib produced durable remissions in some patients that no other drug could replicate. A number relapsed and died after the drug was no longer available, the company said.

Hood and Dr. Catriona Jamieson, a UC San Diego oncologist/researcher, have looked ever since for a way to bring back fedratinib, which led to the launch of Impact Biomedicines.

San Diego’s biggest biotech deal was in 2013 when Life Technologies agreed to be purchased for $13.6 billion by scientific instrumentation company Thermo Fisher, bringing to an end the independent existence of San Diego County's most highly valued biotech company.

Hundreds of San Diego hotel workers marched in downtown San Diego to pressure Marriott hotels to improve pay and working conditions for low wage workers.

Hundreds of San Diego hotel workers marched in downtown San Diego to pressure Marriott hotels to improve pay and working conditions for low wage workers.

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Hundreds of San Diego hotel workers marched in downtown San Diego to pressure Marriott hotels to improve pay and working conditions for low wage workers.

Hundreds of San Diego hotel workers marched in downtown San Diego to pressure Marriott hotels to improve pay and working conditions for low wage workers.

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The Supreme Court on Monday struck down a federal law that bars gambling on football, basketball, baseball and other sports in most states, giving states the go-ahead to legalize betting on sports.

The Supreme Court on Monday struck down a federal law that bars gambling on football, basketball, baseball and other sports in most states, giving states the go-ahead to legalize betting on sports.

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Viasat is a global communications company working to connect the unconnected throughout the world. As part of our mission, we're bringing low-cost, high-speed satellite internet to rural towns throughout Mexico. We believe that everyone, everywhere deserves the opportunity to add their voice to the global conversation. (Courtesy of Viasat)

Viasat is a global communications company working to connect the unconnected throughout the world. As part of our mission, we're bringing low-cost, high-speed satellite internet to rural towns throughout Mexico. We believe that everyone, everywhere deserves the opportunity to add their voice to the global conversation. (Courtesy of Viasat)

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San Diego has agreed to sell 16 lots in Nestor for $1 each, in the pursuit of affordable housing. The nonprofit San Diego Community Land Trust plans to build three and four-bedroom homes there for people with moderate incomes. That means a family of five with an income of up to $102,750.

San Diego has agreed to sell 16 lots in Nestor for $1 each, in the pursuit of affordable housing. The nonprofit San Diego Community Land Trust plans to build three and four-bedroom homes there for people with moderate incomes. That means a family of five with an income of up to $102,750.

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Toys R Us still sells about 20% of the toys bought in the U.S., according to an analyst at Jefferies LLC.

Toys R Us still sells about 20% of the toys bought in the U.S., according to an analyst at Jefferies LLC.